In the context of human society, a family (from Latin: familia) is a group of people related either by consanguinity (by recognized birth), affinity (by marriage or other relationship), or co-residence (as implied by the etymology of the English word "family") or some combination of these. The purpose of families is to maintain the well-being of its members and of society. Ideally, families would offer predictability, structure, and safety as members mature and participate in the community. In most societies, it is within families children acquire socialization for life outside the family. Additionally, as the basic unit for meeting the basic needs of its members, it provides a sense of boundaries for performing tasks in a heterosexual environment, ideally builds a person into a functional adult, transmits culture, and ensures continuity of humankind with precedents of knowledge. Anthropologists generally classify most family organizations as matrifocal (a mother and her children); conjugal (a wife, her husband, and children, also called the nuclear family); avuncular (for example, a grandparent, a brother, his sister, and her children); or extended (parents and children co-reside with other members of one parent's family). Members of the immediate family may include spouses, parents, grandparents, brothers, sisters, sons, and daughters. Members of the extended family may include aunts, uncles, cousins, nephews, nieces, and siblings-in-law. Sometimes these are also considered members of the immediate family, depending on an individual's specific relationship with them. Sexual relations among the members are regulated by rules concerning incest such as the incest taboo. The word "family" can be used metaphorically to create more inclusive categories such as community, nationhood, global village, and humanism. The field of genealogy aims to trace family lineages through history. The family is also an important economic unit studied in family economics. .